Newfangled, digital 3-D movies are exceedingly popular these days. But those Hollywood blockbusters are just the latest trend in a long line of virtual reality experiences that began ages ago. To get closer to the genesis of virtual reality, you have to dig up history that's far older than James Cameron's "Avatar".

For our purposes, the term virtual reality (also known as VE, or virtual environment) refers to technologies that immerse a person in an artificial environment that seems at least partially real, and may involve user interactivity. A 3-D movie, for example, is a form of virtual reality because it provides more visual depth for our eyes than a regular, 2-D film. And an interactive video game system, such as a Nintendo Wii, that uses motion detection controllers with vibration feedback is also a type of virtual environment.

The initial concepts of virtual reality were born long before moving pictures or computer games. Some scientists and historians suspect that human fascination with a form of virtual reality began with artists, including those who lived in caves.

Many prehistoric dwellings feature drawings and illustrations on interior walls. It's not hard to imagine family elders pointing to those drawings and passing along stories under torchlight, with the shadows and light making it seem as though the people and animals in the pictures were moving.

Similarly, talented painters in ancient Greece and Rome crafted intricate, panoramic paintings that brought outdoor scenes inside, either as decorations or as backdrops for theater. By changing the scale and size of objects in those paintings, the artists could trick a viewer's eyes into thinking a space was bigger or smaller than it really was.

Contemporary virtual reality technology relies on accumulated knowledge and techniques to create convincing alternate realities. As such, it's hard to credit a single person with the invention of virtual reality. However, one of the first people to pull together an all-encompassing virtual experience was Morton Heilig.

Born in 1926, Heilig was a consummate tinkerer who studied engineering, philosophy, art, film, and communications from New York City, to Chicago, to Paris. He enjoyed film but felt that projected movies still needed refinement to make them more engaging.

Keep reading to discover how Heilig transformed 2-D films into a more engrossing form of entertainment -- and how his inventions helped propel virtual reality technologies forward.